Regrinding structure for hammermill

ABSTRACT

An improvement in the structure of the grinding chamber of a hammermill consisting of a transverse channel extending across the lower portion of the grinding chamber of the hammermill, said channel serving as a barrier to momentarily halt and deflect upwardly increments of the material passing through said grinding chamber whereby said increments of material are engaged by the hammer blades to have such an effective impact from said blades as to be again crushed or pulverized as on the order of the same extent as in connection with the first impact of said material by said blades upon said material first entering said grinding chamber. A very effective crushing or pulverizing action takes place with the material being at a relative standstill when impacted by said hammer blades.

[ REGRINDING STRUCTURE FOR HAMMERMILL Sept. 9, 1975 [57] ABSTRACT Animprovement in the structure of the grinding chamber of a hammermillconsisting of a transverse channel extending across the lower portion ofthe grinding chamber of the hammermill, said channel serving as abarrier to momentarily halt and deflect upwardly increments of thematerial passing through said grinding chamber whereby said incrementsof material are engaged by the hammer blades to have such an effectiveimpact from said blades as to be again crushed or pulverized as on theorder of the same extent as in connection with the first impact of saidmaterial by said blades upon said material first entering said grindingchamber. A very effective crushing or pulverizing action takes placewith the material being at a relative standstill when impacted by saidhammer blades.

4 Claims, 6 Drawing Figures [76] Inventor: Robert P. Olson, Rt. No, 2,Box

657, Mound, Minn. 55364 [22] Filed: May 8, I974 [2]] Appl, No: 467,997

[52] US. Cl. 241/73; 241/883; 24l/]86.3 [51] Int. Cl. B02C 13/04 [58]Field of Search 241/73, 86.1, 88.3, 88.4, 24l/89.l, 89.2, I86 R, [86.1,I862, 186.3, I89 A [56] References Cited UNITED STATES PATENTS 99l,4775/l9ll Buchanan 24l/88.3 l l25,l37 l/l9l5 Liggctt 4 4 241/883 l,53l 8563/l925 Frickey 24l/73 l,75l,009 3/1930 Liggett 4 24l/73 21509.242 5/1950Miller et al. 24l/73 X l 1 E F 66 65' a,

P I l 68 I l I l r PATENTED 9W5 3,904,134

sum 2 BF 2 FIE: E

w LA -25- REGRINDING STRUCTURE FOR HAMMERMILL BACKGROUND AND SUMMARY OFTHE INVENTION The invention herein relates to an improvement in theeffective result of the grinding operation in the grinding chamber of ahammermill.

The hammers or cutting blades in a hammermill are carried by a rotor andare carried or driven at a speed of some 17 to 20 thousand fpm (feet perminute) whereas free flowing material coming into the grinding chamberenters at the rate of some 60 fpm. Hence. the initial contact of thehammer blade with the material in view of their relative rates of speedrepresents an explosive impact of the blades with the material with aresulting very effective crushing action taking place at the instant ofsaid impact. Once the material entering the grinding chamber has madeone revolution, it accelerates very rapidly in approaching the speed ofthe hammer blades whereas the subsequent impact of the blades on thematerial is less effective than the first explosive impact. The purposeof the invention herein is to provide a structure whereby there may besubsequent impact between the hammer blades and the material beingground on the order of said first mentioned impact. The first impact ofthe hammer blade with the material being ground may be regarded as afirst grinding effort. The invention herein provides at least onesubsequent such grinding effort to increase substantially the grindingefficiency or effectiveness of the action within the grinding chamber.

It is an object of this invention therefore to provide means within thegrinding chamber whereby there will be a subsequent impact between thehammer blades and the material being ground on the order of the firstexplosive impact between said blades and the material upon entering thegrinding chamber.

It is another object of this invention to provide means within thegrinding chamber of a hammerrnill whereby successive increments of thematerial being centrifuged therein are deflected and momentarily haltedin at least one point of travel in moving through the grinding chamberand in being brought to a relative stop there result successiveexplosive impacts between the hammer blades and the relativelystationary quantities of material thus deflected. said impacts being onthe order of the first impact of said blades with said material uponfirst coming into the grinding chamber whereby there results aneffective regrinding of said material.

More generally stated. it is an object of this invention to provide atransverse channel extending across the lower portion of the grindingchamber ofa hammerrnill wherein successive quantities of the materialmoving centrifugally through said chamber engage and become deflectedupwardly at said channel in sufficient quantity for crushing engagementby said hammer blades whereby there results what may be regarded as aregrinding effort.

It is a specific object of this invention to provide structure withinthe grinding chamber of a hammermill to have more than the initialexplosive or crushing impact between the grinding member and thematerial therein with successive increments of said material beingdeflected and momentarily stopped well within the grinding chamber toprovide a subsequent grinding impact between said grinding member andsaid material.

These and other objects and advantages of the invention will be setforth in the following description made in connection with theaccompanying drawings in which like reference characters refer tosimilar parts throughout the several views and in which:

FIG. 1 is a view in side elevation of a hammermill structure;

FIG. 2 is a broken view in vertical section on an enlarged scale takenon line 22 of FIG. 1 as indicated;

FIG. 3 is a broken view in vertical section on an enlarged scale takenon line 33 of FIG. 2 as indicated;

FIG. 4 is a broken view of a detail of structure on an enlarged scale invertical section taken on line 4-4 of FIG. 3;

FIG. 5 is a broken view of a detail of structure in vertical sectiontaken on line 55 of FIG. 4 as indicated; and

FIG. 6 is a broken view of a detail of structure on an enlarged scale inhorizontal section taken on line 66 of FIG. 4 as indicated.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings. ahammermill structure is indicated by the reference numeral 10. Only somuch of the structure of said hammerrnill will be disclosed anddescribed as is believed necessary to support a full description of thestructure comprising the subject matter of the invention herein.

Said hammermill comprises a housing 12, a motor 13 and a drive shaft 15.Said housing has a door 18 and locking means 20 in connection therewith.

Said housing 12 comprises a top wall 22, side walls 23 and 24, a bottomwall 25 and an underlying supporting frame 27.

Within said housing 12 is a chamber 30. Disposed through said top wall22 is an inlet chute 32 having diverging plate members 33 and 34depending inwardly of said chamber 30. Extending downwardly from saidbottom wall 25 is a discharge outlet 36.

Said drive shaft 15 extends inwardly of said housing 12 and carries atits inner end a rotor 38 of a conventional type having mounted thereonhammer blades 40.

Adjacent the bottom of said chamber carried on the back wall 42 thereofand extending forwardly thereof are a pair of spaced brackets 45 and 46.Said brackets respectively have stub bearing shafts 47 and 48 to whichare pivoted the lower end portions of screen retaining members 51 and52. Said screen retaining members are frame-like in form here shown todefine a grinding chamber of tear-drop configuration and having theirupper end portions 51:: and 51h overlying the depending end portions ofthe plate members 33 and 34. Screen members 53 and 54 of appropriatemesh are respectively disposed within said frame members SI and 52. Theupper end portions of said frame members are engaged by locking orclamping members and 61. Said clamping member 60 comprises a platemember 63 secured to the upper end portion of said retaining frameportion 51 and having a tubular rod 64 from which projects a screw rod65 through the wall 23 being retained by an outer tubular boss orhousing 66 through which said rod is threaded and said rod has at itsouter end an operating handle 68. Rotation of said handle swings saidretaining member 51 about said shaft 47 to draw the retaining memberaway from said plate member 33 to release the screen member retainedthcrebetween or to secure the same in operating position, as the casemay be. Said member 6] is of identical structure as of said member 60.Said retaining members 51 and 52 and the screens 53 and 54 disposedtherein form the side walls of a grinding chamber 70.

Shown carried by said depending plate member 34 is a deflection member72 having its outer wall 73 angled to form a guide for incoming materialto direct the same in the direction of rotation of said rotor 38. Saidwall 73 has a small inward flange 74 formed at its lower end.

Extending transversely of the bottom of said grinding chamber 70 betweensaid brackets 45 and 46 is a material deflection member 76 shown here inthe form of a grooved or channel member which is here shown sccured andsupported at one end to the back wall 42 of said housing by a dependingflange portion 77 as by bolts 78. Said channel member may take onvarious transverse configurations and is here shown being U- shaped inform.

Carried at the inner side of said door 18 spaced therefrom by posts 19is a plate member 21 which overlies the screen retaining members 51 and52 and forms the front wall of the grinding chamber 70.

The material entering the grinding chamber 70 and being ground thereinis indicated by the reference char acter A.

OPERATION The invention herein relates to increasing the effectivenessof the grinding operation of the grinding chamber of a hammermill andrelates to increasing the capability and effectiveness of its grindingeffort.

Material for grinding which is gravity fed into the grinding chamber ofa hammermill enters the grinding chamber at a rate on the order of aspeed of some 60 fpm. The rotor 38 has an average operating speedbetween l700 and 2100 RPM which represents a speed of the tips of theblades 40 on the order of something over 17,000 fpm. It is the firstimpact at which the most crushing or pulverizing in the grindingoperation takes place for the material is at a relative standstillcompared to the speed of the hammer blades. It is desirable to have asubsequent impact between the hammer blades and the material as severeor as crushing as said first impact.

The structure comprising the subject matter of the invention herein isdesigned to provide an additional opportunity for a grinding effortwhich is substantially equivalent to the crushing effect of the firststep above described.

The member 76 as located represents the essential element of theinvention in providing a channel across the lower portion of thegrinding chamber. As a result of the centrifugal action provided by thehammer blades. the material to be ground is driven against the innersurface of the screen. As increments of this material approach andengage the channel member 76, said increments are deflected upwardly bya wall of said channel and are thus momentarily halted relative to thespeed of the hammer blades and at this point said increments of materialthus halted are subjected to the explosive impact or crushing effect ofthe first hammer blades engaging them. This is a continuous action withsuccessive quantities of the material being deflected and brought to arelative halt so that with the passage of each hammer blade over thisarea, said material by impact of said hammer blades is crushed andpulverizcd and in being continuously subjected to this explosive impact.the result of this is that a very effective grinding or pulverizing ofthe material takes place. The successive quantities of material beingdeflected up wardly by the channel member 76 may be likened to arecurrence of the first or initial grinding effort or in effect beingsubjected to a regrinding effort.

The deflection member 72 as a result of its bottom wall 75 and flangeportion 74 creates another area which serves to cause a deflection and amomentary halt of material which again is subjected to an explosive orcrushing impact of the hammer blades. Hence, as a result of the functionof the members 76 and 72, what in effect takes place within the grindingchamber adjacent thcse members might be regarded as a regrinding ofmaterial resulting in a very effective pulvcrization or reduction ofsaid material.

The channel member 76 alone or together with the member 72 as here shownsubstantially reduces the time otherwise required to sufficiently grindmaterial to a desired reduction in size. This invention has materiallyincreased the efficiency and the capability of the grinding operation ofa hammermill and has substantially decreased the time required forgrinding.

It will of course be understood that various changes may be made inform, details, arrangement and proportions of the parts withoutdeparting from the scope of the invention herein which, generallystated. consists in an apparatus capable of carrying out the objectsabove set forth. in the parts and combinations of parts disclosed anddefined in the appended claims.

What is claimed is:

1. The grinding chamber of a hammermill, having in combination an inletchute feeding material into said grinding chamber.

a grinding member in said grinding chamber rotating at a speedsubstantially greater than the speed of travel of said material feedingthercinto.

a channel forming member extending transversely of said grindingchamber,

said channel member having a portion thereof dcflecting upwardlyincrements of said material received therein passing through saidgrinding chamber and halting the forward movement thereof, and

said grinding member impacting said upwardly deflected increments ofmaterial.

2. The structure set forth in claim 1, wherein said channel member issubstantially U-shaped in cross section having a chamber therein toreceive said material, and

a side wall of said channel member deflecting upwardly said material.

3. The structure set forth in claim I, wherein said channel memberextending across the bottom of said grinding chamber in close proximityto the path of said grinding member, and

means removably securing said channel member.

4. The structure set forth in claim 1, including a deflecting means fora second deflection of material comprising a depending plate membercarried by a side wall portion of said chamber. and

a flange portion of said plate member stopping and deflecting incrementsof material passing through said chamber slowing down the passage ofsaid material for impaction by said grinding member.

1. The grinding chamber of a hammermill, having in combination an inletchute feeding material into said grinding chamber, a grinding member insaid grinding chamber rotating at a speed substantially greater than thespeed of travel of said material feeding thereinto, a channel formingmember extending transversely of said grinding chamber, said channelmember having a portion thereof deflecting upwardly increments of saidmaterial received therein passing through said grinding chamber andhalting the forward movement thereof, and said grinding member impactingsaid upwardly deflected increments of material.
 2. The structure setforth in claim 1, wherein said channel member is substantially U-shapedin cross section having a chamber therein to receive said material, anda side wall of said channel member deflecting upwardly said material. 3.The structure set forth in claim 1, wherein said channel memberextending across the bottom of said grinding chamber in close proximityto the path of said grinding member, and means removably securing saidchannel member.
 4. The structure set forth in claim 1, including adeflecting means for a second deflection of material comprising adepending plate member carried by a side wall portion of said chamber,and a flange portion of said plate member stopping and deflectingincrements of material passing through said chamber slowing down thepassage of said material for impaction by said grinding member.